Method and apparatus for transmitting and receiving data in a mimo system

ABSTRACT

The present invention relates to a method and apparatus for transmitting and receiving data. A data transmission method from a sender terminal to a receiver terminal in a MIMO system using a variable frequency band according to one embodiment of the present invention comprises: repeatedly generating a signal field depending on a frequency band that is applied to the transmission of a data frame; generating a data field including the data; generating a data frame including the signal field and the data field; and transmitting the data frame to the receiver terminal. The present invention is advantageous in that a signal field which is transmitted together with the data being transmitted from the sender terminal to the receiver terminal in the MIMO system can be sent more efficiently.

TECHNICAL FIELD

The present invention relates to a method and apparatus for transmittingand receiving data and, more particularly, to a method and apparatus fortransmitting and receiving data in a multiple input multiple output(MIMO) system.

BACKGROUND ART

A wireless local area network (WLAN) basically supports a basic serviceset (BSS) mode including an access point (AP) serving as a connectionpoint of a distribution system (DS) and a plurality of stations (STAs),however, not APs, or an independent BSS (IBSS) mode including onlystations (STAs) (hereinafter, AP and STA will be referred to as a‘terminal’).

In a wireless communication system using multiple antennas, i.e., a MIMOsystem, a channel capacity is increased according to an increase in thenumber of antennas, and frequency efficiency can be enhancedaccordingly. The MIMO system may be classified into the following twotypes of systems: a first one is a single user (SU)-MIMO, in whichmultiple streams are transmitted only to a single user, and a second oneis a multi-user (MU)-MIMO in which multiple streams are transmitted tomultiple users by canceling interference between users by an AP.

The MU-MIMO is advantageous in that it can obtain even a multi-userdiversity gain along with the increase in channel capacity. Also, theMU-MIMO scheme can simultaneously transmit multiple streams to multipleusers by using the same frequency band, increasing throughput incomparison to an existing communication scheme. In general, throughputof the wireless communication system can be increased by increasing thefrequency band, but a system cost is disadvantageously increasedaccording to the increase in the frequency band. Meanwhile, the MU-MIMOscheme does not increase the frequency band but its complexity isdrastically increased in comparison to the existing communicationscheme. Thus, in the standard such as 802.11ac, methods forsimultaneously employing the MU-MIMO technique while using a variablefrequency according to a surrounding situation have been researched.

In the wireless communication system in which multiple antenna streamsare simultaneously transmitted to several users while using a variablefrequency band, a data field and a signal field including informationregarding the corresponding data field are transmitted. The signal fieldis divided into the following two types of fields. The first is a commonsignal field including information commonly applied to users. The secondis a dedicated signal field including information individually appliedto each user. The common signal field may be recognized by every userwho belongs to a common user group or who may not belong to the commonuser group. Also, the common signal field is used for auto-detection fordiscriminating by which communication system a transmitted data framehas been generated (namely, it is used for auto-detection fordiscriminating a communication system by which a transmitted data framewas generated), so that, the common signal field is required to havecompatibility. Thus, there is a limitation in changing the format or theconfiguration of the common signal field.

The common signal field is transmitted through a simple iterativestructure to an SNR gain and a frequency diversity gain. However, thededicated signal field cannot obtain both the SNR gain and the frequencydiversity gain although such a simple iterative structure as that of thecommon signal field is used.

DISCLOSURE Technical Problem

The present invention provides a method and apparatus for effectivelytransmitting a signal field which is transmitted together when atransmission terminal transmits data to a reception terminal in amultiple input multiple output (MIMO) system.

The foregoing and other objects, features, aspects and advantages of thepresent invention will be understood and become more apparent from thefollowing detailed description of the present invention. Also, it can beeasily understood that the objects and advantages of the presentinvention can be realized by the units and combinations thereof recitedin the claims.

Technical Solution

In an aspect, a method for transmitting data by a transmission terminalto a reception terminal in a multiple input multiple output (MIMO)system using a variable frequency band includes iteratively generating asignal field according to a frequency band applied to transmission of adata frame, generating a data field including the data, generating adata frame including the signal field and the data field, andtransmitting the data frame to the reception terminal.

In another aspect, a method for receiving data by a reception terminalfrom a transmission terminal in a multiple input multiple output (MIMO)system using a variable frequency band includes receiving a data frameincluding a signal field and a data field, and obtaining the dataincluded in the data field by using the signal field, wherein the signalfield is iteratively included in the signal field according to afrequency band applied to transmission of the data frame.

In another aspect, a transmission device transmitting data to areception terminal in a multiple input multiple output (MIMO) systemusing a variable frequency band includes a signal field generation unititeratively generating a signal field according to a frequency bandapplied to transmission of a data frame, a data field generation unitgenerating a data field including the data, a data frame generation unitgenerating a data frame including the signal field and the data field,and a transmission unit transmitting the data frame to the receptionterminal.

In another aspect, a reception device receiving data from a transmissionterminal in a multiple input multiple output (MIMO) system using avariable frequency band includes a reception unit receiving a data frameincluding a signal field and a data field, and a data obtaining unitobtaining the data included in the data field by using the signal field,wherein the signal field is iteratively included in the signal fieldaccording to a frequency band applied to transmission of the data frame.

Advantageous Effects

According to embodiments of the present invention, a signal field, whichis transmitted together when a transmission terminal transmits data to areception terminal in a MIMO system, can be effectively transmitted.

Also, in transmitting a dedicated signal field in the MU-MIMO system,the performance of the signal field is enhanced and a transmission timeis reduced by utilizing a user's frequency band and the number ofstreams, whereby a large amount of information can be effectivelytransmitted by using the signal field.

DESCRIPTION OF DRAWINGS

FIG. 1 shows the structure of a data frame used in a datatransmission/reception method according to an embodiment of the presentinvention.

FIG. 2 shows an embodiment in which an access point (AP) transmits fourstreams through MU-MIMO beamforming by using four antennas in an 80 MHzfrequency band and two stations (STA) receive the streams by using twoantennas, respectively.

FIG. 3 shows the structure of a VHT-SIG B field when a station (STA)receives one stream in a 20 MHz frequency band.

FIG. 4 shows the structure of a VHT-SIG B field when a station (STA)receives four streams in a 20 MHz frequency band.

FIG. 5 shows the structure of a VHT-SIG B field when a station (STA)receives four streams in an 80 MHz frequency band.

FIG. 6 shows the structure of a VHT-SIG B field having two symbols whena station (STA) receives one stream in a 20 MHz frequency band.

FIG. 7 shows the structure of a VHT-SIG B field having two symbols whena station (STA) receives four streams in a 20 MHz frequency band.

FIG. 8 shows the structure of a VHT-SIG B field having one symbol when astation (STA) receives four streams in a 20 MHz frequency band.

FIG. 9 shows an embodiment in which SIG Bs are transmitted over twosymbols in a similar manner to that of a VHT-SIG A when a station (STA)receives one stream in a 40 MHz frequency band.

FIG. 10 shows the structure of a VHT-SIG B field having one symbol whena station (STA) receives one stream in a 40 MHz frequency band.

FIG. 11 shows an embodiment of applying a data transmission methodaccording to the present invention to a case in which a station (STA)receives two streams in a 20 MHz frequency band.

FIG. 12 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives three streams in a 20 MHz frequency band.

FIG. 13 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives four streams in a 20 MHz frequency band.

FIG. 14 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives one stream in a 40 MHz frequency band.

FIG. 15 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives two streams in a 40 MHz frequency band.

FIG. 16 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives three streams in a 40 MHz frequency band.

FIG. 17 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives one stream in an 80 MHz frequency band.

FIG. 18 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives two streams in an 80 MHz frequency band.

FIG. 19 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives three streams in an 80 MHz frequency band.

FIG. 20 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives four streams in an 80 MHz frequency band.

FIG. 25 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which data istransmitted via two non-contiguous multi-channels in an 80 MHz frequencyband.

FIG. 26 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which data istransmitted via three non-contiguous multi-channels in an 80 MHzfrequency band.

FIG. 27 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which data istransmitted by using one QPSK symbol in a 20 MHz frequency band.

FIG. 28 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which data istransmitted by using one QPSK symbol in a 40 MHz frequency band.

FIG. 29 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which data istransmitted by using one QPSK symbol in an 80 MHz frequency band.

FIG. 30 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which data istransmitted via two non-contiguous multi-channels by using one QPSKsymbol in an 80 MHz frequency band.

FIG. 31 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which data istransmitted via three non-contiguous multi-channels by using one QPSKsymbol in an 80 MHz frequency band.

FIG. 32 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a first stream istransmitted by using two space-time streams and a second stream istransmitted as it is in a 20 MHz frequency band.

FIG. 33 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a first stream istransmitted by using two space-time streams and a second stream istransmitted as it is in a 40 MHz frequency band.

FIG. 34 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which one stream istransmitted by using two space-time streams in a 20 MHz frequency band.

FIG. 35 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a first stream istransmitted by using two space-time streams and a second stream istransmitted as it is in a 20 MHz frequency band.

FIG. 36 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a first stream istransmitted by using two space-time streams and a second stream istransmitted as it is in a 40 MHz frequency band.

FIG. 37 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives one stream in a 40 MHz frequency band.

FIG. 38 shows an embodiment of applying a data transmission methodaccording to the present invention to a case in which a station (STA)receives two streams in a 40 MHz frequency band.

FIG. 39 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives three streams in a 40 MHz frequency band.

FIG. 40 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives four streams in a 40 MHz frequency band.

FIG. 41 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives one stream in an 80 MHz frequency band.

FIG. 42 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives two streams in an 80 MHz frequency band.

FIG. 43 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives three streams in an 80 MHz frequency band.

FIG. 44 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives four streams in an 80 MHz frequency band.

FIG. 45 shows a bit allocation of a VHT-SIG B when the VHT-SIG B has alength of 26 bits in a 20 MHz band, has a length of 27 bits in a 40 MHzband, and has a length of 29 bits in an 80 MHz band.

FIG. 46 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives four streams in a 20 MHz frequency band, when the numbers ofbits of the VHT-SIG B are allocated as shown in FIG. 45 .

FIG. 47 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives four streams in a 40 MHz frequency band, when the numbers ofbits of the VHT-SIG B are allocated as shown in FIG. 45 .

FIG. 48 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives four streams in an 80 MHz frequency band, when the numbers ofbits of the VHT-SIG B are allocated as shown in FIG. 45 .

FIG. 49 shows an embodiment in which the VHT-SIG B has a length of 26bits in a 20 MHz band, 27 bits in a 40 MHz band, and 29 bits in an 80MHz band, and some of the reserved bits included in a service field areused as CRC bits.

FIG. 50 shows a bit allocation of the VHT-SIG B when the VHT-SIG B has alength of 26 bits in a 20 MHz band, 27 bits in a 40 MHz band, and 29bits in a 80 MHz band in SU-MIMO.

FIG. 51 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives four streams in a 20 MHz frequency band, when the numbers ofbits of the VHT-SIG B are allocated as shown in FIG. 50 .

FIG. 52 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives four streams in a 40 MHz frequency band, when the numbers ofbits of the VHT-SIG B are allocated as shown in FIG. 50 .

FIG. 53 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives four streams in an 80 MHz frequency band, when the numbers ofbits of the VHT-SIG B are allocated as shown in FIG. 50 .

FIG. 54 shows an embodiment in which the VHT-SIG B has a length of 26bits in a 20 MHz band, 27 bits in a 40 MHz band, and 29 bits in an 80MHz band, and some of the reserved bits included in a service field areused as CRC bits.

FIG. 55 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives four streams in a 20 MHz frequency band, when cyclic delaydiversity (CDD) technique is used and different delay is applied to eachantenna.

FIG. 56 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives four streams in a 40 MHz frequency band, when a CDD techniqueis used and different delay is applied to each antenna.

FIG. 57 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives four streams in an 80 MHz frequency band, when a CDD techniqueis used and different delay is applied to each antenna.

FIG. 58 shows the configuration of a transmission terminal according toan embodiment of the present invention.

FIG. 59 shows the configuration of a reception terminal according to anembodiment of the present invention.

FIG. 60 is a flow chart illustrating an embodiment of a method fortransmitting data by a transmission terminal according to an embodimentof the present invention.

FIG. 61 is a flow chart illustrating an embodiment of a method forreceiving data by a reception terminal according to an embodiment of thepresent invention.

MODE FOR INVENTION

The foregoing and other objects, features, aspects and advantages of thepresent invention will be described in detail in conjunction with theaccompanying drawings, and accordingly, a person skilled in the art towhich the present invention pertains will easily implement the technicalconcept of the present invention. In describing the present invention,if a detailed explanation for a related known function or constructionis considered to unnecessarily divert the gist of the present invention,such explanation will be omitted but would be understood by thoseskilled in the art. The embodiments of the present invention will now bedescribed with reference to the accompanying drawings, in which likenumbers refer to like elements in the drawings.

FIG. 1 shows the structure of a data frame used in a datatransmission/reception method according to an embodiment of the presentinvention.

In FIG. 1 , L-STF and L-LTF, training fields, and L-SIG, a signal field,are the same as those of a data frame used in an existing 802.11. Theframe illustrated in FIG. 1 further includes fields dedicated for highspeed wireless communication, i.e., very high throughput (VHT). VHT-STFand VHT-LTF are VHT-dedicated training fields, and VHT-SIG A and VHT-SIGB are VHT-dedicated signal fields.

The data frame of FIG. 1 includes data fields VHT-DATA including datatransmitted to several users, respectively. VHT-SIG B includesinformation regarding each of the data fields. For example, VHT-SIG Bmay include information regarding the length of useful data included inthe VHT-DATA field, information regarding a modulation and coding scheme(MCS) of the VHT-DATA field, and the like. Since the VHT-SIG B fieldincludes information regarding each user, it corresponds to a dedicatedsignal field. Meanwhile, the VHT-SIG A field is a common signal fieldtransmitted to be recognized by every user.

FIG. 2 shows an embodiment in which an access point (AP) transmits fourstreams through MU-MIMO beamforming by using four antennas in an 80 MHzfrequency band and two stations (STA) receive the streams by using twoantennas, respectively.

In the embodiment of FIG. 2 , VHT-SIG A field, a common signal field, isiterated four times so as to be transmitted as one stream, and MU-MIMOis not applied to this transmission. In FIG. 2 , the presence of theL-SIG field in front of VHT-SIG A field is to maintain backwardcompatibility with existing legacy equipment. A VHT-TF field is used toperform channel estimation in using MU-MIMO beamforming, and may have aresolvable or non-resolvable form.

VHT-SIG A includes common information commonly applied to two stations(STA). Also, VHT-SIG A, having a different structure from a signal fieldgenerated in legacy equipment, is used for auto-detection of VHTequipment. Here, VHT-SIG A is simply iteratively transmitted in units of20 MHz frequency, whereby both an SNR gain and a frequency diversitygain can be obtained.

In comparison, VHT-SIG B, a dedicated-signal field, includinginformation applied to each of the stations STA, is transmitted. Thus,VHT-SIG B is not required to be transmitted by using the simpleiterative structure like the VHT-SIG A does. Also, even when VHT-SIG Bis transmitted by using the simple iterative structure like VHT-SIG A,VHT-SIG B cannot obtain both an SNR gain and a frequency diversity gain.

In order to solve the problems, the present invention provides a method,apparatus, and a data field configuration capable of enhancingtransmission efficiency by using a new method, rather than the simpleiterative method like the existing VHT-SIG A field in transmitting theVHG-SIG B field.

FIG. 3 shows a structure of the VHT-SIG B field when a station (STA)receives one stream in a 20 MHz frequency band. Here, the VHT-SIG B(referred to as an ‘SIG B’, hereinafter) is modulated according to BPSKand has one OFDM symbol. In FIG. 3 , since there is only one SIG B, itmay be transmitted as it is.

FIG. 4 shows a structure of the VHT-SIG B field when a station (STA)receives four streams in a 20 MHz frequency band. In the embodiment ofFIG. 4 , four SIG Bs are transmitted. Here, in case in which the SIG Bis transmitted in a simple iterative manner like the VHT-SIG A, if achannel environment of particular subcarriers of OFDM becomes worse inMU-MIMO beamforming, the iterative four bits are all placed in the samesituation. Thus, an SNR gain according to the iteration four times maybe obtained, but a frequency diversity effect cannot be obtained.

Thus, in an embodiment of the present invention, different interleavingis applied to the SIG Bs of the stream 1 to stream 4. When the same bitsof a coded codeword of the SIG Bs is included in a different subcarrierof a different stream and transmitted, both the SNR gain and thefrequency diversity gain can be obtained, improving transmissionperformance.

FIG. 5 shows a structure of the VHT-SIG B field when a station (STA)receives four streams in an 80 MHz frequency band. In the embodiment ofFIG. 5 , although the SIG B is simply iterated in a frequency band, boththe SNR gain and the frequency diversity gain can be obtained. Thus,maximum performance can be obtained by simply iterating the schemeapplied to the four streams in the embodiment of FIG. 4 .

The method described with reference to FIGS. 4 and 5 may be applied inthe same manner to 40 MHz frequency band or 160 MHz band and when thenumber of streams is two or three.

Meanwhile, information included in the VHT-SIG B field is required to bestably transmitted compared with information included in the VHT-DATAfield. Thus, in general, the VHT-SIG B field is transmitted by using aBPSK modulation and a low coding rate, or the like, thus beingprotected. Thus, the method described with reference to FIGS. 4 and 5may protect the VHT-SIG B more than necessary.

In the case of VHT-SIG A, it must be necessarily recognized in units of20 MHz at a receiver (or a receiving end). Thus, the VHT-SIG A must beiteratively transmitted by a corresponding symbol length regardless ofthe number of symbols. However, iteratively transmitting the VHT-SIG Bby a corresponding symbol length may be problematic in terms of theforegoing transmission performance and efficiency.

FIG. 6 shows a structure of the VHT-SIG B field having two symbols whena station (STA) receives one stream in a 20 MHz frequency band. In FIG.6 , the SIG B is modulated according to BPSK and has two OFDM symbols.Here, since there is only one SIG B, it may be transmitted as it is.

FIG. 7 shows a structure of a VHT-SIG B field having two symbols when astation (STA) receives four streams in a 20 MHz frequency band. Like theembodiment of FIG. 4 , both SNR gain and frequency diversity gain can beobtained by applying different interleaving to streams.

However, if sufficient performance can be obtained without having toiterate the SIG B, the method of FIG. 7 may not be an effectivetransmission because the SIG B is transmitted over two symbols. Thus,the following transmission method is considered.

FIG. 8 shows a structure of the VHT-SIG B field having one symbol when astation (STA) receives four streams in a 20 MHz frequency band. In theembodiment of FIG. 8 , the SIG B information, which has occupied twosymbols when transmitted as one stream in the 20 MHz frequency band, canbe effectively transmitted by only one symbol.

When the frequency band applied to a transmission of a data frameextends, a method similar to FIG. 8 may be considered. FIG. 9 shows anembodiment in which SIG Bs are transmitted over two symbols in a similarmanner to that of a VHT-SIG A when a station (STA) receives one streamin a 40 MHz frequency band. In the embodiment of FIG. 9 , since SIG Bsare transmitted over two symbols although sufficient performance can beobtained without iterating the SIG B, it is not effective.

FIG. 10 shows a structure of the VHT-SIG B field having one symbol whena station (STA) receives one stream in a 40 MHz frequency band. In thiscase, the SIG B information, which has occupied two symbols whentransmitted as one stream in the 40 MHz frequency band, can beeffectively transmitted through one symbol.

In this manner, when the VHT-SIG B has two symbols when transmitted asone stream in the 20 MHz frequency band, even though the number ofstreams is increased or the frequency band extends, the VHT-SIG B can beeffectively transmitted by using one symbol. Also, the foregoing methodsmay extend as follows.

FIG. 11 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives two streams in a 20 MHz frequency band. FIG. 12 shows anembodiment of applying the data transmission method according to thepresent invention to a case in which a station (STA) receives threestreams in a 20 MHz frequency band. In the embodiment of FIG. 12 ,stream 3 is configured of B1 corresponding to an even number bit of acodeword of the SIG B1 and B2 corresponding to an odd number bit of acodeword of SIG B2. The stream 3 transmitted thusly may be combined at areceiver.

FIG. 13 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives four streams in a 20 MHz frequency band. In the embodiment ofFIG. 13 , SIG B1 is iterated in streams 1 and 3, and SIG B2 is iteratedin streams 2 and 4. In this case, a simple iteration cannot obtain afrequency diversity gain, so different interleaving may be applied toeach stream in order to enhance transmission performance as mentionedabove.

FIG. 14 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives one stream in a 40 MHz frequency band. FIG. 15 shows anembodiment of applying the data transmission method according to thepresent invention to a case in which a station (STA) receives twostreams in a 40 MHz frequency band. FIG. 16 shows an embodiment ofapplying the data transmission method according to the present inventionto a case in which a station (STA) receives three streams in a 40 MHzfrequency band. Different interleaving may be applied to each stream ofFIGS. 14, 15, and 16 .

FIG. 17 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives one stream in an 80 MHz frequency band. FIG. 18 shows anembodiment of applying the data transmission method according to thepresent invention to a case in which a station (STA) receives twostreams in an 80 MHz frequency band. FIG. 19 shows an embodiment ofapplying the data transmission method according to the present inventionto a case in which a station (STA) receives three streams in an 80 MHzfrequency band. FIG. 20 shows an embodiment of applying the datatransmission method according to the present invention to a case inwhich a station (STA) receives four streams in an 80 MHz frequency band.Different interleaving may be applied to each stream of FIGS. 17, 18,19, and 20 .

FIG. 21 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives one stream in a 160 MHz frequency band. FIG. 22 shows anembodiment of applying the data transmission method according to thepresent invention to a case in which a station (STA) receives twostreams in a 160 MHz frequency band. FIG. 23 shows an embodiment ofapplying the data transmission method according to the present inventionto a case in which a station (STA) receives three streams in a 160 MHzfrequency band. FIG. 24 shows an embodiment of applying the datatransmission method according to the present invention to a case inwhich a station (STA) receives four streams in a 160 MHz frequency band.Different interleaving may be applied to each stream of FIGS. 21, 22,23, and 24 .

The transmission method according to an embodiment of the presentinvention as described above can be applicable when a data frame istransmitted by using a multi-channel. FIG. 25 shows an embodiment ofapplying the data transmission method according to the present inventionto a case in which data is transmitted via two non-contiguousmulti-channels in an 80 MHz frequency band. FIG. 26 shows an embodimentof applying the data transmission method according to the presentinvention to a case in which data is transmitted via threenon-contiguous multi-channels in an 80 MHz frequency band. Differentinterleaving may be applied to each stream of FIGS. 25 and 26 .

The transmission method according to an embodiment of the presentinvention as described above can be applicable when the VHT-SIG B fielduses one QPSK symbol instead of two BPSK symbols. FIG. 27 shows anembodiment of applying the data transmission method according to thepresent invention to a case in which data is transmitted by using oneQPSK symbol in a 20 MHz frequency band. FIG. 28 shows an embodiment ofapplying the data transmission method according to the present inventionto a case in which data is transmitted by using one QPSK symbol in a 40MHz frequency band. FIG. 29 shows an embodiment of applying the datatransmission method according to the present invention to a case inwhich data is transmitted by using one QPSK symbol in an 80 MHzfrequency band. FIG. 30 shows an embodiment of applying the datatransmission method according to the present invention to a case inwhich data is transmitted via two non-contiguous multi-channels by usingone QPSK symbol in an 80 MHz frequency band. FIG. 31 shows an embodimentof applying the data transmission method according to the presentinvention to a case in which data is transmitted via threenon-contiguous multi-channels by using one QPSK symbol in an 80 MHzfrequency band. Different interleaving may be applied to each stream ofFIGS. 27, 28, 29, 30, and 31 .

The transmission method according to an embodiment of the presentinvention as described above can be applicable when one stream istransmitted as a space-time block code (STBC) (or an Alamouti code)through two antennas. In this case, the VHT-SIG B field may betransmitted as the STBC in the same manner as that of the data field, orthe VHT-SIG B field may be transmitted by using one of two space-timestreams. In the former case, STBC-related information should be includedin the VHT-SIG A in advance and transmitted, and in the latter case, theSTBC-related information may be included in the VHT-SIG B andtransmitted.

FIG. 32 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a first stream istransmitted by using two space-time streams and a second stream istransmitted as it is in a 20 MHz frequency band. FIG. 33 shows anembodiment of applying a data transmission method according to thepresent invention to a case in which a first stream is transmitted byusing two space-time streams and a second stream is transmitted as it isin a 40 MHz frequency band.

FIG. 34 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which one stream istransmitted by using two space-time streams in a 20 MHz frequency band.FIG. 35 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a first stream istransmitted by using two space-time streams and a second stream istransmitted as it is in a 20 MHz frequency band. FIG. 36 shows anembodiment of applying the data transmission method according to thepresent invention to a case in which a first stream is transmitted byusing two space-time streams and a second stream is transmitted as it isin a 40 MHz frequency band. In the embodiment of FIG. 36 , the streamscan be effectively transmitted by using one symbol.

The data transmission method according to an embodiment of the presentinvention as described above may also be applicable when only a portionof a stream is transmitted by using the STBC. The data transmissionmethod according to an embodiment of the present invention as describedabove may also be applicable when the VHT-SIG B uses three or more OFDMsymbols in transmitting one stream in a 20 MHz band.

A data transmission and reception method according to another embodimentof the present invention will now be described.

As described above, in an embodiment of the present invention, adedicated signal field is iteratively effectively transmitted in afrequency or stream domain, to thus obtain a maximum diversity gain.This method can be applicable to a case in which a frame is transmittedby using channel bonding in a 40 MHz or 80 MHz bandwidth.

When two 20 MHz frequency bands are bonded to form a 40 MHz frequencyband, a portion of a frequency tone, which is generally used as a guardband, or the like, can be used as a frequency tone for a datatransmission. For example, in the case of 802.11n, the number of datatransmission frequency tones in the 20 MHz band is 52, and the number ofdata transmission frequency tones in the 40 MHz band is 108. Namely, in802.11n, the use of channel bonding results in an increase in the numberof four data transmission frequency tones in the 40 MHz band. Thus, thenumber of transmission frequency tones can be further increased in an 80MHz band by using channel bonding based on the same principle.

The foregoing VHT-SIG B field transmission scheme of the presentinvention can be applicable to a frame transmission using channelbonding. Here, the increased data transmission frequency tones can beused to increase the amount of data included in a signal field or theiteration number of signal fields. Namely, the method according to thepresent invention can be applicable even to a case in which the numberof bits of the SIG B in the 40 MHz band or the 80 MHz band is greaterthan the number of bits of the SIG B in the 20 MHz band.

FIG. 37 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives one stream in a 40 MHz frequency band. FIG. 38 shows anembodiment of applying the data transmission method according to thepresent invention to a case in which a station (STA) receives twostreams in a 40 MHz frequency band. FIG. 39 shows an embodiment ofapplying the data transmission method according to the present inventionto a case in which a station (STA) receives three streams in a 40 MHzfrequency band. FIG. 40 shows an embodiment of applying the datatransmission method according to the present invention to a case inwhich a station (STA) receives four streams in a 40 MHz frequency band.Different interleaving may be applied to each stream of FIGS. 37, 38,39, and 40 .

FIG. 41 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives one stream in an 80 MHz frequency band. FIG. 42 shows anembodiment of applying the data transmission method according to thepresent invention to a case in which a station (STA) receives twostreams in an 80 MHz frequency band. FIG. 43 shows an embodiment ofapplying the data transmission method according to the present inventionto a case in which a station (STA) receives three streams in an 80 MHzfrequency band. FIG. 44 shows an embodiment of applying the datatransmission method according to the present invention to a case inwhich a station (STA) receives four streams in an 80 MHz frequency band.Different interleaving may be applied to each stream of FIGS. 41, 42,43, and 44 .

When the number of bits of the SIG B and the number of frequency tonesused in transmission are not in a mutually multiple relationship, somefrequency tones may remain after iterating the SIG B. In this case, amethod of iterating only a portion of the SIG B or padding may be used.This method can be applicable when the information of SIG B is increasedaccording to an increase in the frequency bandwidth from 20 MHz to 40MHz and to 80 MHz.

In general, when the frequency bandwidth is increased, the amount ofdata transmitted in the same duration is increased. Accordingly, whenlength information of transmitted data, or the like, is included in theVHT-SIG B and transmitted, the length of the VHT-SIG B itself isincreased. In this case, a bit allocation of the VHT-SIG B is changed byfrequency bandwidth and the VHT-SIG B may be iterated according to thenumber of transmittable frequency tones, thus enhancing transmissionefficiency. For example, it is assumed that the number of available datatones in a 20 MHz band is 26 bits, the number of available data tones ina 40 MHz band is 54 bits, and the number of available data tones in an80 MHz band is 117 bits. In this case, the length of the VHT-SIG B is 26bits in the 20 MHz band, 27 bits in the 40 MHz band, and 29 bits in the80 MHz band. FIG. 45 shows a bit allocation in this case.

FIG. 46 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives four streams in a 20 MHz frequency band, when the numbers ofbits of the VHT-SIG B are allocated as shown in FIG. 45 . FIG. 47 showsan embodiment of applying the data transmission method according to thepresent invention to a case in which a station (STA) receives fourstreams in a 40 MHz frequency band, when the numbers of bits of theVHT-SIG B are allocated as shown in FIG. 45 . FIG. 48 shows anembodiment of applying the data transmission method according to thepresent invention to a case in which a station (STA) receives fourstreams in an 80 MHz frequency band, when the numbers of bits of theVHT-SIG B are allocated as shown in FIG. 45 . Different interleaving maybe applied to each stream of FIGS. 46, 47, and 48 . The presentinvention can be applicable even when the number of transmitted streamsis changed in the embodiments of FIGS. 46, 47, and 48 .

The bit allocation of VHT-SIG B in FIG. 45 includes tail bits for aconvolutional code. However, the VHT-SIG B of FIG. 45 does not includeCRC bits for determining whether or not a codeword has an error, makingit difficult to obtain reliability of data. However, in the case of 20MHz band, since there is no extra bit in the VHT-SIG B, some (4 to 8bits) of the reserved bits included in a service field of a data fieldmay be used as the CRC bit as shown in FIG. 49 .

When the bit allocation as shown in FIG. 49 is used, the CRC issimultaneously applied to the SIG B and a scrambler seed. Thus, CRCcalculation with respect to a variable length is required for eachfrequency band. The VHT-SIG B field uses a low modulations scheme andcoding rate (BPSK 1/2), and is available for an iterative coding tofrequency and an antenna domain, so it has high reliability. Meanwhile,the service field uses the modulation scheme and coding rate used fortransmission of data, as it is, so its reliability is relativelyvariable and generally has low reliability compared with the VHT-SIG B.In this case, the use of a CRC can detect an error of informationincluded in the VHT-SIG B field and an error of a scrambler seed. Thus,when an error of the scrambler seed is detected, the operation of PHYand MAC layers can be stopped, obtaining an effect of reducing powerconsumption.

The foregoing method can be applicable to SU-MIMO. In SU-MIMO, theVHT-SIG A may relatively have extra bits. Thus, in SU-MIMO, the MCSbits, which are included in the VHT-SIG B field, can be included in theVHT-SIG A field. In SU-MIMO, the number of antennas in use may beincreased, so the number of bits of the field indicating a data lengthmay be increased. FIG. 50 shows a bit allocation of the VHT-SIG B whenthe VHT-SIG B has a length of 26 bits in a 20 MHz band, 27 bits in a 40MHz band, and 29 bits in a 80 MHz band in SU-MIMO.

FIG. 51 shows an embodiment of applying a data transmission methodaccording to the present invention to a case in which a station (STA)receives four streams in a 20 MHz frequency band, when the numbers ofbits of the VHT-SIG B are allocated as shown in FIG. 50 . FIG. 52 showsan embodiment of applying a data transmission method according to thepresent invention to a case in which a station (STA) receives fourstreams in a 40 MHz frequency band, when the numbers of bits of theVHT-SIG B are allocated as shown in FIG. 50 . FIG. 53 shows anembodiment of applying a data transmission method according to thepresent invention to a case in which a station (STA) receives fourstreams in an 80 MHz frequency band, when the numbers of bits of theVHT-SIG B are allocated as shown in FIG. 50 . Different interleaving maybe applied to each stream of FIGS. 51, 52, and 53 . The presentinvention can be applicable even when the number of transmitted streamsis changed in the embodiments of FIGS. 51, 52, and 53 .

When the bit allocation of VHT-SIG B field as shown in FIG. 50 is used,the VHT-SIG B field includes tail bits for a convolutional code.However, the VHT-SIG B of FIG. 50 does not include a CRC bits fordetermining whether or not a codeword has an error, making it difficultto obtain reliability of data. However, in the case of 20 MHz band,since there is no extra bit in the VHT-SIG B, some (4 to 8 bits) of thereserved bits included in a service field of a data field may be used asthe CRC bit as shown in FIG. 54 .

When the bit allocation as shown in FIG. 54 is used, the CRC issimultaneously applied to the SIG B and a scrambler seed. Thus, CRCcalculation with respect to a variable length is required for eachfrequency band. The VHT-SIG B field uses a low modulations scheme andcoding rate (BPSK 1/2), and is available for an iterative coding tofrequency and an antenna domain, so it has high reliability. Meanwhile,the service field uses the modulation scheme and coding rate used fortransmission of data, as it is, so its reliability is relativelyvariable and generally has low reliability compared with the VHT-SIG B.In this case, the use of a CRC can detect an error of informationincluded in the VHT-SIG B field and an error of a scrambler seed. Thus,when an error of the scrambler seed is detected, the operation of PHYand MAC layers can be stopped, obtaining an effect of reducing powerconsumption.

In the data transmission and reception method according to the presentinvention as described above, when the VHT-SIG B field is transmitted,different interleaving is applied to the frequency domain with respectto mutually different transmission streams, thereby obtaining a maximumdiversity gain even in the antenna domain. In this respect, however, inorder to obtain similar effects while slightly reducing the complexity,cyclic delay diversity (CDD) technique may be used to transmit theVHT-SIG B field, without applying different interleaving to eachtransmission stream. In this case, the same data is transmitted by eachtransmission antenna, and here, a different delay is applied to eachantenna.

FIG. 55 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives four streams in a 20 MHz frequency band, when cyclic delaydiversity (CDD) technique is used and different delay is applied to eachantenna. FIG. 56 shows an embodiment of applying the data transmissionmethod according to the present invention to a case in which a station(STA) receives four streams in a 40 MHz frequency band, when a CDDtechnique is used and different delay is applied to each antenna. FIG.57 shows an embodiment of applying the data transmission methodaccording to the present invention to a case in which a station (STA)receives four streams in an 80 MHz frequency band, when a CDD techniqueis used and different delay is applied to each antenna. Different delayis applied to each stream of FIGS. 55, 56, and 57 . The presentinvention can be applicable even when the number of transmitted streamsis changed in the embodiments of FIGS. 55, 56, and 57 .

Also, spreading matrix to the antenna domain having a size of (number oftransmission antennas and number of transmission antennas) may beadditionally applicable to the VHT-SIG B transmission scheme of thepresent invention. When different interleaving is applied to eachstream, the spreading matrix when multi-stream is applied can beapplicable, and when each stream is transmitted by applying delaythereto, the spreading matrix when a single stream is applied can beapplicable.

FIG. 58 shows the configuration of a transmission terminal according toan embodiment of the present invention.

A transmission terminal 5802 includes a signal field generation unit5804, a data field generation unit 5806, a data frame generation unit5808, and a transmission unit 5810. The signal field generation unit5804 iteratively generates a signal field according to a frequency bandapplied to transmission of a data frame. The data field generation unit5806 generates a data field including data to be transmitted to areception terminal. The data frame generation unit 5808 generates a dataframe including the signal field generated by the signal fieldgeneration unit 5804 and the data field generated by the data fieldgeneration unit 5806. The transmission unit 5810 transmits the dataframe generated by the data frame generation unit 5808 to the receptionterminal.

Here, the signal field may include a length field indicating the lengthof a data field, and the length field may have a length which differsaccording to a frequency band applied to transmission of a data frame.Also, the signal field may include a modulation and coding scheme (MCS)field indicating a modulation method and a coding method of the datafield. Also, the signal field may be a dedicated signal field fortransferring information regarding each user. The data frame may includea cyclic redundancy check (CRC) field for detecting an error of thesignal field.

FIG. 59 shows the configuration of a reception terminal according to anembodiment of the present invention.

A reception terminal 5902 includes a reception unit 5904 and a dataobtaining unit 5906. The reception unit 5904 receives a data frameincluding a signal field and a data field.

Here, the signal field may include a length field indicating the lengthof a data field, and the length field may have a length which differsaccording to a frequency band applied to transmission of a data frame.Also, the signal field may include a modulation and coding scheme (MCS)field indicating a modulation method and a coding method of the datafield. Also, the signal field may be a dedicated signal field fortransferring information regarding each user. The data frame may includea cyclic redundancy check (CRC) field for detecting an error of thesignal field.

The data obtaining unit 5906 obtains data included in the data field byusing the signal field included in the received data frame. Here, thedata obtaining unit 5906 may obtain the data by using the length field,the MCS field, or the like, included in the signal field. Also, the dataobtaining unit 5906 may detect an error of the signal field by using theCRC field included in the data frame.

FIG. 60 is a flow chart illustrating the process of a method fortransmitting data by a transmission terminal according to an embodimentof the present invention.

First, a signal field is iteratively generated according to a frequencyband applied to transmission of a data frame (6002). Also, a data fieldincluding data to be transmitted to a reception terminal is generated(6004). And then, a data frame including the generated signal field anddata field is generated (6006). Thereafter, the generated data frame istransmitted to a reception terminal (6008).

Here, the signal field may include a length field indicating the lengthof the data field, and the length field may have a length which differsaccording to a frequency band applied to transmission of the data frame.Also, the signal field may include a modulation and coding scheme (MCS)field indicating a modulation method and a coding method of the datafield. Also, the signal field may be a dedicated signal field fortransferring information regarding each user. The data frame may includea cyclic redundancy check (CRC) field for detecting an error of thesignal field.

FIG. 61 is a flow chart illustrating the process of a method forreceiving data by a reception terminal according to an embodiment of thepresent invention.

First, a data frame including a signal field and a data field isreceived (6102). Here, the signal field may include a length fieldindicating the length of the data field, and the length field may have alength which differs according to a frequency band applied totransmission of the data frame. Also, the signal field may include amodulation and coding scheme (MCS) field indicating a modulation methodand a coding method of the data field. Also, the signal field may be adedicated signal field for transferring information regarding each user.The data frame may include a cyclic redundancy check (CRC) field fordetecting an error of the signal field.

And then, data included in the data field is obtained by using thesignal field included in the received data frame (6104). In this case,the reception terminal may obtain data by using the length field, theMCS field, or the like, included in the signal field. Also, thereception terminal may detect an error of the signal field by using aCRC field included in the data frame.

According to embodiments of the present invention, when a dedicatedsignal field is transmitted in the MU-MIMO system, the performance ofthe signal field is enhanced and a transmission time is reduced byutilizing the user frequency band and the number of streams, whereby alarge amount of information can be effectively transmitted by using thesignal field.

Although the present invention has been described with reference toexemplary embodiments and the accompanying drawings, it would beappreciated by those skilled in the art that the present invention isnot limited thereto but various modifications and alterations might bemade without departing from the scope defined in the claims and theirequivalents.

1. A communication apparatus, comprising: a circuitry which isconfigured to: determine a bandwidth of a communication channel; causethe apparatus to receive at least a part of a frame through thecommunication channel, wherein the frame comprises a first field and asecond field, wherein the first field precedes the second field, whereinthe first field comprises a first set of bits indicating a length ofdata, and the second comprises the data; determine a number of bits ofthe first set of bits based on the bandwidth of the communicationchannel; and determine the length of the data based on the first set ofbits.
 2. The communication apparatus of claim 1, wherein the framefurther comprises a third field and a fourth field, wherein the thirdfield precedes the fourth field, and the fourth field precedes the firstfield, wherein each of the first, third and fourth fields comprisescontrol information for the frame.
 3. The communication apparatus ofclaim 2, wherein the third field comprises a legacy signal (L-SIG)field, the fourth field comprises a Very High Throughput Signal A(VHT-SIG-A) field, and the first field comprises a Very High ThroughputSignal B (VHT-SIG-B) field.
 4. The communication apparatus of claim 3,wherein the second field further comprises a cyclic redundancy check(CRC) information related to the first field.
 5. The communicationapparatus of claim 4, wherein the bandwidth of the communication channelis 20*2^((n-1)) MHz, n is an integer greater than 0, and the first setof bits is repeated 2^((n-1)) times in the VHT-SIG-B field.
 6. Acommunication device for a station, the communication device comprising:a circuitry which is configured to: determine a bandwidth of acommunication channel; cause the station to receive at least a part of aframe through the communication channel, wherein the frame comprises afirst field and a second field, wherein the first field precedes thesecond field, wherein the first field comprises a first set of bitsindicating a length of data, and the second comprises the data;determine a number of bits of the first set of bits based on thebandwidth of the communication channel; and determine the length of thedata based on the first set of bits.
 7. The communication device ofclaim 6, wherein the frame further comprises a third field and a fourthfield, wherein the third field precedes the fourth field, and the fourthfield precedes the first field, wherein each of the first, third andfourth fields comprises control information for the frame.
 8. Thecommunication device of claim 7, wherein the third field comprises alegacy signal (L-SIG) field, the fourth field comprises a Very HighThroughput Signal A (VHT-SIG-A) field, and the first field comprises aVery High Throughput Signal B (VHT-SIG-B) field.
 9. The communicationdevice of claim 8, wherein the second field further comprises a cyclicredundancy check (CRC) information related to the first field.
 10. Thecommunication device of claim 9, wherein the bandwidth of thecommunication channel is 20*2^((n-1)) MHz, n is an integer greater than0, and the first set of bits is repeated 2^((n-1)) times in theVHT-SIG-B field.